Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net income	$ 84,734	$ 39,755	$ 10,812
Adjustment to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	69,086	69,179	64,507
Amortization of contract acquisition costs	1,002	3,015	1,678
Amortization of debt issuance costs	1,083	992	745
Imputed interest expense and fair value adjustments to contingent consideration	2,339	10,217	51
Provision for doubtful accounts	1,711	3,679	458
(Gain) loss on disposal of assets	189	111	3,694
Gain on sale of business	0	0	(908)
Impairment losses	3,735	1,452	5,322
Impairment of equity investment	0	15,632	0
Gain (adjustment) on bargain purchase of a business	0	(685)	0
Non-cash loss on assets held for sale reclassified to assets held and used	0	1,616	0
Deferred income taxes	(1,376)	(7,975)	16,777
Excess tax benefit from equity-based awards	(1,231)	(635)	(2,192)
Equity-based compensation expense	12,814	12,145	11,852
(Gain) loss on foreign currency derivatives	(140)	1,524	(681)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable	29,608	29,985	(59,284)
Prepaids and other assets	27,413	(30,438)	(19,266)
Accounts payable and accrued expenses	97,268	11,713	18,968
Deferred revenue and other liabilities	(90,246)	7,063	60,619
Net cash provided by operating activities	237,989	168,345	113,152
Cash flows from investing activities
Proceeds from sale of long-live assets	382	34	39
Purchases of property, plant and equipment	(60,776)	(43,450)	(51,958)
Proceeds from sale of business	0	0	636
Investments in non-marketable equity investments	0	(2,119)	(1,384)
Acquisitions, net of cash acquired of $4,547, $4,530, and $5,997, respectively	(102,457)	(2,027)	(116,320)
Net cash used in investing activities	(162,851)	(47,562)	(168,987)
Cash flows from financing activities
Proceeds from line of credit	1,152,750	2,162,400	2,293,587
Payments on line of credit	(1,144,750)	(2,224,400)	(2,166,887)
Payments on other debt	(11,855)	(5,989)	(6,041)
Payments of contingent consideration and hold back payments to acquisitions	(5,902)	(1,349)	(1,409)
Dividends paid to shareholders	(28,739)	(25,346)	(21,531)
Payments to noncontrolling interest	(4,950)	(2,925)	(3,645)
Capital contribution from noncontrolling interest	3,362	0	0
Proceeds from exercise of stock options	0	208	2,150
Tax payments related to issuance of restricted stock units	(5,471)	(4,643)	(5,397)
Payments of debt issuance costs	(1,819)	(35)	(918)
Purchase of treasury stock	0	0	(18,328)
Net cash (used in) provided by financing activities	(47,374)	(102,079)	71,581
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(410)	(14,904)	3,427
Increase (decrease) in cash, cash equivalents and restricted cash	27,354	3,800	19,173
Cash, cash equivalents and restricted cash, beginning of period	78,237	74,437	55,264
Cash, cash equivalents and restricted cash, end of period	105,591	78,237	74,437
Supplemental disclosures
Cash paid for interest	13,108	17,456	11,727
Cash paid for income taxes	36,316	39,984	18,813
Non-cash investing and financing activities
Acquisition of long lived assets through finance leases	3,731	15,018	9,836
Acquisition of equipment through increase in accounts payable, net	$ 881	$ 339	$ 97